I have a handgun that i bought from a guy. it didn't have paper work and I'm not 21. how much trouble could i?

So i bought a .22 Ruger New Bearcat from a guy and it doesn't have paperwork and I'm not 21. So basically i bought a gun. I'm 18 and don't have any criminal history or anything. If i got caught with it by the police, what could happen to me? Could i get fined? Go to jail? I live in Ohio also.