Hey Scord, not sure you got an answer to your question. You know, we seem to take things for granted when all is going well and we forget we were once in desperate need of help. I hope I can help. If the sore area is very close, almost touching your stoma, it's from the stuff coming out of the stoma making contact with bare, unprotected skin. If it's a centimeter or so away from the stoma I think a change in your prep can help. I try to allow no space between the stoma and the flange without "choking" the stoma and I use Cavilon barrier wipes on the skin surrounding it. The sore needs to get healed and there are lots of folks here to tell you how to accomplish that.
Good luck,
Mike