Played tennis yesterday night, my opponent was a bit late and I was tired, so I lay on a court for ~10 minutes (yesterday was the first day this season when it was relatively cold, before that we would often play at 95F/35C) and didn't warm up properly. I think that that, along with me arching my back on the serve way more than usual (have been experimenting with the serve), contributed to me developing a stiff back in the beginning of the match. I never experienced it before, it wasn't too bad, although clearly limiting, and I wasn't in pain, so we still played a three-setter; it didn't get worse but didn't get better, either. Took a hot bath yesterday, it feels slightly better today. My question is - will I be potentially putting my back health at risk by hitting in the next few days (just hitting, no serves) or should I better wait till it goes away completely? I did the initial googling but the results are inconclusive. I'm a 34yo guy in a good shape, reasonably flexible, strong back muscles, NTRP 4.5 I guess, usually play tennis 6-7 times a week for 2-3 hours.