Huge very dark purple bruise right thigh discovered 2 days ago and is getting bigger, no pain or tenderness feel a small knot under skin?

Bruise: You don't remember bumping into something? A large bruise without trauma is unlikely. The knot you feel is probably a blood clot under the skin that will dissipate on its own. The medications you listed should not cause your bruise. It will look worse before it looks better. If you think it was indeed spontaneous, you should really have your doctor check a CBC on you.