I most definitely agree with 'ashlito' look after those calfs especially if you do a lot of rounds pounding those bags with your shins or even knees for that matter!,many a time I have hit the Thai pads as hard as I can for a few rounds and then worked on other areas such as boxing or clinching forgetting how much work I have done on the legs and not stretching afterwards only to wake up the day after with aching calfs from the constant pounding and impact made on the bags or pads. I do feel it important to make sure you have a good stretch after as well as before your workout to lessen the risk of damaged muscles,if you do Muay Thai there is a lot more impact and stress in the calf area due to the powerful kicks used so be very careful.Even a few rounds of kneeing creates stress on the calfs because you are constantly on the balls of your feet and again the impact created by the knees pounding on the bags or pads will tighten those important muscles!
'ashlito' I hope you do not give up and you eventually get back to kicking again it's so frustrating not being able to train properly!