Cool all the best to you man although the ass thing makes it sus but you do what you feel won't hurt your relationship and is better for you

Well judging by your story there's two possible explanations here

1. She likes you and the message was a "hint" even showing you her ass tattoo I mean man that's really private stuff
2. She just comfortable enough and trusted you enough to know that you won't try anything and knows you touched her boob by accident so it's OK don't worry man

Just talk to her if you want or see if her behaviour changes towards you

Damn man I'd suggest seeing a dentist immediately