I am sorry to hear that you are suffering from multiple health issues, and hope that these will improve. I am certainly happy that you will be speaking with your doctor
shortly about this bump, as bumps should always be promptly reviewed with your physician unless they have a known cause and resolve shortly (like hitting your head on a cupboard!). As for what this lump could be, you certainly seem to be describing something that is in the most superficial layers of the skin. In most cases, these are not signs of a deeper problem, but are rather local reactions to something that is happening, such as a local skin infection. Unfortunately, without more information about your overall health and without the ability to see the lump and characterize it better (pain, recent injury
, etc), it is difficult to anticipate exactly what this might be. As you suggested that you will be seeing your doctor shortly, it may be appropriate to observe this spot carefully for signs of change so that you can describe it fully to your doctor when you visit. Please follow up with your doctor as planned, or sooner if you become more concerned.