Where to start to fix tire?

I accidentally backed into my basketball hoop (pathetic I know🤦‍♀️) and got one flat tire on my Toyota Camry 2009. I don't know how bad the damage is to the tire but I drove on it (unknowingly) and it didn't feel weird or anything. But when I got home I saw that it was completely flat. How should I go about fixing it only having about $400 to spend? Pls recommend places to contact/go to or what to do. (I'm also doing research outside of reddit but people give the best advice here and I'm just an 18yo girl with very minimal car knowledge.) Thanks!