Nipples :-)))

So I have a question about nipples. Ik that every girl has different boobs and nipples but I was just thinking my nipples are tiny in comparison to my sisters. They do go hard and stick out every now and again so I don't think they are inverted and when my boyfriend uses his mouth over then it feels amazing. I'm 14 and size 10C but my sister is twelve and she has bigger boobs. Should I be concerned, will they grow as I get older and does anyone else have unusually small nipples?