Originally Posted by
Santiims
I'm afraid stretching won't help much at this point. You were too hard on yourself in the gym. When returning to the gym after an extended period of inactivity, you should really go easy on yourself, even if it feels you can do more weights etc. Basically what you have is too much lactic acid in your muscles, and the most common places for it to appear is indeed in the spot you described.
In my case the best treatment is to just rest a bit and in a few days the pain will be gone. But if you feel like taking additional treatment measures, feel free to google lactic acidosis treatment and go from there.
Source: Personal experience.