I opened a tin can and ate something with my hands, which made them greasy. Now holding a weapon is impossible, and so is wearing rings. I tried #wipe but it seems that's only for the face. How would I wipe my hands?
You need to find a towel and apply it.
If you lack a towel, the effect should go away in due time without you needing to do anything. According to Wooble in the comments, this is specifically up to 15 turns.