Evans has puffy nipples, so maybe the rubbing was a way to make them look normal.
If you see someone with a small bit of gyno when their nipples are "hard" you can't see the gyno. When they are not, you can see the puffiness.
****
On a side note, that was probably the hardest punch KO I have ever seen. Rashad put his whole body into that punch and landed it solid. Chuck was sleeping. It wasn't only of those "it rattled me" punches. It was a lullaby punch.