I Was Bit By Something Yesterday Evening And I Do

I was bit by something yesterday evening and I do not know what it was. The bite feels similar to a mosquito bite however it continues to itch and has now swelled up to the size of a softball. It is hot to the touch and hard. It is located just above my knee on the back side of my lower thigh. I have taken Benadryl and put cortisone and ice on it. Should I be concerned or will the symptoms subside?