Over the course of the last couple weeks I've noticed my 3 year old male, Nubbin, has developed a little lump on his side. Its fixed in place but clearly only in the skin, not like its part of some organ or something underneath. Its rather hard, like a BB under his skin. It doesn't seem to be growing or bothering him and its so small I hesitate to get it drained and chance infection. Should I just let it go? Any idea what it could be?