What Are The Large Itchy Bumps On The Finger?

I have large bumps on my fingers that itch when hands get warm, especially in the evening at bedtime. The bumps have become large raised, dry and itchy. No fluid is in them. Some times they seem to look like they are going away, but like today mid day all the sudden like the flip of a switch, my fingers started itching. I went to my regular doctor, and he have me antibiotic as my little finger has become swollen, and a steroid cream, and the use of ceravale lotion. He's not sure what it may be, and suggested blood tests to check my immune system. (I dont understand the connection, but have yet to get blood tests. I've never had this happen to my hands. The is no sign of bites, and not on palms of hands, just fingers. As well as no where else on my body.