Rub it in
Definition 1 of 2
Pro Tip 1/3Emotional Impact
This phrase can hurt feelings by highlighting someone's misfortune or failures. 
After losing the game, having the victory constantly mentioned really rubbed it in.
Pro Tip 2/3Conversational Context
Used among friends or acquaintances to point out they're being irritating by overemphasizing. 
Okay, I get it, I was wrong - don't rub it in.
Pro Tip 3/3Informality
The phrase is casual and may not be suitable for formal or professional settings. 
In a business meeting, instead of saying 'don't rub it in,' you might say, 'Let's not dwell on the past.'