I was biten by something on my hand it looks like a small cluster of pimples it itch and its hard under the skin?

Local allergic rxn: is common from many different types of insect bites as well as contact to a chemical such as poison ivy and if you only have one spot, then it is unlikely to be something ingested, which would cause a more generalized reaction. Both will cause itching instead of pain, which is more likely related to infection. For itch, cold compresses, oral antihistamines (Benadryl) and hydrocortisone cream.

Allergic reaction: It is the allergic reaction to the bite, you may take benadryl (diphenhydramine) and apply hydrocortisone ointment on this area. The itch and swelling should go away in 2-3 days. If you get more pimples or any other problem then see your doctor.