Turbo Tax didn't autofill my info from last year like it usually does. As a result, I submitted my taxes and forgot to include my SSDI income. What do I do now?

I have an SSA-1099 that I need to add, and it will bump my taxes owed up by $2000. It says my returns have been accepted. Do I attempt to amend the return? Will I be fined? And if I can't pay the full amount, what happens?