If you fall behind on payments, you'll see an impact on your credit. Even a single missed payment can lower your credit score. Depending on the terms of your loan agreement, your lender may also charge you late fees. If you keep missing payments, your loan will eventually go into default and your lender might send your account to collections or take legal action against you.
It's a good idea to talk to your lender if you're unable to make a payment due to financial difficulty. Most lenders would rather work with you to find a solution rather than let the loan go into default. Your lender may let you defer a payment to a future date, or change the terms of your loan to accommodate a smaller monthly payment.