Yes after I gave birth to my childre, which were natural, my stomach muscles were sore for a couple of weeks. Simply because all of the contractions and everything. And I could only imagine that with a c-section you would be more sore. Try using warm compresses and see if that will relax your muscles some, if not try to sneek in a soak in the tub. Good luck
The best thing to do is to go back to your OBGYN for a follow-up appointment to let them know. There are a lot of factors they will take into account to determine if this is normal or not.
Yes, I had sore tummy muscles for a while afterwards. Also, I'm 4 months post csection and STILL have numbness from my bellybbutton down. It's not %100 numb but the skin is numb all the way from my bellybutton to my incision line. My first csection didn't leave me numb this long.