I don’t have a computer with me. So how can I restore without computer

Unfortunately you can't. You need a computer. And I tunes (or finder if using a mac with Catalina or later)

If you can borrow a friend or family member’s computer that is running iTunes, do that. If you don’t, make an appointment at an Apple Store or an AASP and ask for their help.

I’m sorry, but you will need a computer in order to fix it. There is no other way.