Hard bump under skin by bikini line is slightly discolored. i am on birth control, and i've heard it can be a hormone thing. what should i do?

Need more info: Can you send us a pic of your skin bump? How long have you noticed it for? Has it changes appearance since? Is is tender to touch? Since apparently it seems to be bothering you as it should, you should get it checked out by your local doctor and possibly a referral to a derm specialist, who would most likely do a biopsy to confirm diagnosis.

Trauma history?: Was there any previous history of trauma which would cause bruising in that area? Is the area warm? It could be a lymph node in the inguinal area reacting to inflammation from injury or infection. Unless it is enlarging, like a hematoma from bleeding or you have a fever, it can probably wait until tomorrow when you can see a physician at a walk in clinic. If it enlarges, have fever, more pain, ER