How do I deal with under tipping my stylist?

I got my hair done by someone I know but I’m not good friends with him. My color costed $118 and I tipped him $12 and then I found out this was way too low from friends and should be at least 20%. I’m so embarrassed!!! This all just happened and I feel horrible. I tipped through credit card.
Will he see how much I tipped if I paid at the register? And also how should I fix this? Should I send him more money? I feel like I don’t wanna show my face.

Should I message him and mention it, apologize, and promise to tip extra next time??