Think It Is A Strained Hamstring, But Not Sure. Pain

Think it is a strained hamstring, but not sure. Pain in muscle in left thigh but not the large muscle in the back. It is slightly to the outside of the leg from what I would think of as the hamstring.

Tweaked it while swimming about 6 weeks ago. Riding a bike does not seem to bother it, but every time I swim, it is very painful for the next few days.

Can't seem to stretch it out or relieve the pain. Massaging it helps momentarily. Then it often gives a sharp pain. Bending the leg seems to help lessen the pain.

Thoughts?