It’s no skin off my, your, his, etc. nose
Definition 1 of 1
Pro Tip 1/3Indifference Expressed
Shows that you do not care about the outcome or decision someone else is making. 
You can stay or leave, it's no skin off my nose.
Pro Tip 2/3Non-impactful Choices
Use it when someone's choice doesn't have any direct impact or consequences on you. 
Whether you order pizza or sushi for dinner, it's no skin off my nose.
Pro Tip 3/3Informal Context
The phrase is informal, so it's more suitable for casual conversation with friends than in formal settings. 
If he wants to drop out of the football team, it's no skin off my nose.