If it's a stabbing pain near the stoma or even a dull ache, it's something your Dr. needs to know about and soon. It could be anything, or it could be nothing, but it's always better to be safe than sorry on something like this. For me, if I had the pain you're having, it's either a hernia, or perhaps a blockage or a pulled muscle.
At any rate, I'd definitely give them a call soon. Good luck and I hope everything is just fine.