Can I put headphones in? (tragus piercing)?

Don't do it yet. I don't think I wore headphones until about a month to six weeks after getting it done. It's got nothing to do with infection, it's more about prolonging the healing process. It's a very sensitive piercing and you shouldn't be moving the barbell or anything right now, just leave it to heal and only move it if strictly necessary for cleaning. If you do play with it you're going to have a really high chance of developing lumps on the piercing later on, and those can be really hard to get rid of.