Conductive hearing loss refers to hearing loss that is not due to nerve damage of the vestibulocochlear nerve (CN VIII). This covers a lot of ground, from wax buildup to tumors. While conductive hearing loss may indicate a number of different problems that need to be treated, the good news is that once the underlying cause is treated hearing will often return. Even if it doesn't, conductive hearing loss can usually be treated through the use of hearing aids. Sensory hearing loss is less likely to be treatable, and can only be remedied with hearing aids up to a certain point.
The causes of conductive hearing loss (CHL) are many and diverse, and often gruesome. Conditions that can cause CHL include, but are not limited to, deformation of the outer ear and ear canal, external otitis, wax buildup, foreign bodies wedged into the ears, cysts, tumors, middle ear infections, cholesteatoma, perforated eardrums, tympanosclerosis, otosclerosis, fixation of the ossicles, and disarticulation of the ossicles. Temporary conductive hearing loss can also be caused by changes in pressure in the middle ear, but this tends to be very temporary unless accompanied by an infection of the middle ear or eustachian tube.
By far, the most common of these problems is an ear infection, particularly in children. Ear infections and the sometimes-resultant perforated eardrum are generally the only of these conditions that can be safely ignored, and only then if they are infrequent and pass within a week (theories on the safety of ignoring ear infections differ from country to country and from doctor to doctor; YMMV). Ironically, these are the most acutely painful; if you have hearing loss without acute pain, you should be at least as concerned as you are about ear infections. Unfortunately, there is no easy way to determine if hearing loss is conductive or sensory without seeing a doctor (or audiologist), unless you are adventurous enough to try Rinne's test at home. And even if you do, you still need to get your ears checked. Going deaf is not the worst thing that can result from ear problems; cancer spreads, and chronic infections can eat their way through the mastoid process and into the brain.
If you go to an audiologist they will do a fairly standard exam. First they will visually examine your ear canal to look for wax build up, a healthy eardrum with no signs of infections behind it, and any irregularities in the pinna or ear canal. Next they will hook you up to some very fancy earphones and ask you to indicate every time you hear a beep; if you have trouble hearing the beep and there is no obvious reason for this, they may put on another headphone that will transmit the beep through bone conduction, to test the nerve cells in your cochlea (if this is impaired, you should head over to sensory hearing loss). Next they will do a tympanogram to test for flexibility in the ear drum; this will in effect also test the pressure behind the eardrum. If there are any problems without an obvious cause, further tests may be done, although at this point much of the further testing to be done for CHL would have to be done by a specialist. Up to this point, none of the tests are painful, although the otoscope used for the visual inspection can be a bit uncomfortable.
In most cases, problems will be solved through an antibiotic for infections or hearing aids for benign causes of hearing loss, but it is important to get things checked out by a professional whether or not you plan on using either of these solutions.