Turberculosis can often manifest itself as a whitish lump, often near the pectoral fins. It is not something treatable, and usually resolves itself. It is not usually fatal unless the fish in question becomes stressed.
Pretty much all the things that could cause this are things that are not treatable by a home aquarist, so I would just watch the spot, and keep an eye on things in general.
I'm sorry about the curt post before, all to often someone posts things on this forum, we try to help, and wind up finding out that the fin rot was caused by african ciclids being kept with angelfish. A tell tale sign is someone not posting tank parameters with their original question.