Remus never really liked to think about Sirius' sexual interludes with other people. He never held it against him, of course, because he had every right to go off with anyone he wanted to. There was just something about this instance that really messed with him. It didn't feel right. And lying there with Sirius, listening to him talk about how wrong it felt for him too just reaffirmed that for Remus.
"I've got some different pain potions," he offered. "Maybe one would help. I've got.. salves and things I use for muscle issues. You could.. try using one." He felt a little awkward about the latter, because of how invasive that would be. Sirius could apply it himself, but just talking about it made his cheeks grow warm. "Just, I'm no stranger to pain, mate. Anything I have is yours to try."