Are nipples supposed to be inwards?

It's not completely uncommon for nipples to be facing inwards, but if they cause you any pain, or anything comes out when you gently squeeze them, I'd suggest seeing a doctor. The only exception to this is if you are pregnant, and what comes out is breast milk. If your nipples facing inwards is bothering you, you can gently squeeze around them with your (clean) thumb and index finger. But if they don't pop out when you squeeze gently like that, then don't force it.