First of all, please do not prick or poke at the bumps. Actually a subcutaneous skin (under the skin) nodule—the size of a pea and firm, is usually due to a neurofibroma (connective and nerve tissue), a ganglion cyst or a lymph node. Conditions causing skin granulomas should be ruled out. Swimming pool granuloma should be looked into first if you swim. This is caused by Mycobacterium marinum bacteria and the test is same as for tuberculosis. Apart from PPD tuberculin test, skin biopsy—the bacteria can also be cultured. Tick bite is one possibility and if you live in an area prone for tick bites, then Lyme's disease should be ruled out by appropriate tests. Pseudolymphoma is another possibility which causes persistent inflammatory nodules. The good thing is that they are usually without symptoms and disappear on their own by 8-9 months. These can be due to calcinosis or calcium deposits if you have received calcium supplements in the past. An autoimmune condition called granuloma annulare is another possibility and hence immunoglobulins and other tests for autoimmune disorders of which rheumatoid arthritis too is one should be looked into. Sarcoidosis, tuberculosis, pseudorheumatoid disease, foreign body granulomas, leprosies, leishmaniasis (parasitic disease caused by bite of sand fly), lupus, hypothyroidism, diabetes, and deep fungal infections should also be looked into. A ganglion can also undergo granulomatous change.
Since a confirmed diagnosis cannot be given on net please consult your doctor regarding this. Hope this helps. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.