Nah should think you will be OK. Got two of the JJ's wimping off at mo cos of the gym meet - 10 days ago!!!
If you took up any new (active) sport you would be aching for a time afterwoods. Canoeing, squash etc. You are using and stretching bits of the body in new ways and directions. And its not gonna like it!!! But will get use to it.
Try some 'proper' stretching exercises before a session.
But as always , if this persists...do see a doctor.