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.
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 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