Provided baby is gaining enough weight there's absolutely no need to supplement feeds with expressed colostrum, formula or anything else. If you choose to do that, it's a choice, not a need. So no, you haven't messed up! If you don't want to give baby the frozen colostrum then you can use it for baths or keep for things like eye infections or cuts/scrapes. You can put it in the bath whenever you want, there's no minimum age or any other requirements
I've been putting waste breast milk in my babies bath since her first ever bath which I did when she was 6 weeks old. I do it every time I put anywhere from 3 to 7oz in. What ever I have as waste (my freezer is full). It's great for skin so you can do it as young as 3 weeks