A Physio will sort it...... I used a Sports Physio near me, about 15 years ago for a hamstring injury.... went out running, far too far for a cyclist to do straight off..... cue damage (fitness does not help)...... anyway, he sorted it within 10 visits. Long term, the only pain I get is in the anchor point to the side of my knee if I over pushed the miles - that's gone now..... riding fixed has done wonders............
I've also been back recently to him (15 years later) for 6 months for my shoulder injury in an RTA, about 18 months ago - spent a fortune, but it kept me cycling.......
If you can get NHS treatment, try and get it.....my GP said I had no chance getting sorted fast, and if I wanted fixing, then go private.