I recommend that you skip Thursday's class. It is not unusual to have swelling and stiffness
when you are starting out new exercises. The trick is to start out slow and work your way up. I would also seek the expert help of a qualified exercise specialist. Having the right nutrients in terms of Vit. C is helpful in healing your sore muscles. A balanced diet is also recommended. Please do not over exert yourself and stretch your limits. Going to your old self and being happy is a sure shot way to feeling better.
I hope this helps. Take care.