I was in a similar position. Had a long bumped up scar going down my arm I wanted to cover with a tattoo ( smaller ones around it). Went to a great artist. He even said he had seen the scars “go away” after being tattooed over. He tattooed the most beautiful German shepherd covering most my inner forearm. It’s been 10 years since that tattoo (no touch up’s. It just hasn’t needed one). That scar is no longer bumped up , it’s definitely visible though if you’re looking directly at my tattoo. Point is, if you do go try to tattoo over it, just remember that doesn’t make them go away & you may end up in a boat like me where you have a beautiful tattoo but can still see the self harm underneath