I Had A Little Scab On My Left Knee. I

I had a little scab on my left knee. I picked at it. 2 days later it swelled up and drained clear fluid. It was painful. Throbbing pain. The inside of my thigh started hurting all the way up to my groin. On Thursday night I went to the clinic. They attempted to drain it but just blood came out. They gave me Bactrim and ibuprofrin 800. On Friday morning I had a bad headache and a little naseau. It is now Sunday night. Fever is gone. Pain on the cut is gone but Im still in as much pain on the inside of my thigh all the way to my groin. Also been feeling lethargic. Not sure whats going on. Also, if i rub the inside of my thigh where the pain is, it is hard all along the area where the pain is. Please help!!