How terrible are your parents?
I had very kind understanding non-violent non-abusive parents, and I still worried GREATLY that they would find out when I had done something that I thought was AWFUL, and the actual reaction was at worst that they were confused why I did something, and made sure I understood that it wasn’t a good thing to do.
I got gum in my hair, slime on things, lost my shoe in a mud swamp, and much worse. I sometimes was afraid what their reaction would be. But they were my parents. They loved me. They’d seen all sorts of things from me and others and done things themselves. There was actually no real reason for them to be mad about it. They just helped me handle it.
Now, there are other parents who sometimes can be really unpleasant and jerkish about things, and everyone is different, but it seems to me that the jerkish ones I know were sort of mostly jerkish, whether there was a decent reason for it or not.
But in any case, it seems like there are probably few things to do about this except tell them what you did, that you know it wasn’t a great thing to do, and ask for help.
How do you do that? You just tell them. (You’re probably only making yourself upset & confused by worrying about it.) Then it’ll all be over soon enough, except possibly for the funny story about the time you got slime in your hair and tried to cut it yourself. :-)