what to apply to regrow hair on bald spot?

Answer 1

Any hair lotion or tonic with ingredient minoxidil has been medically proven effective. they come with various intenisty 2% 3% 5% and more.
You need to know that this will be a long-term medication, so choose a brand that is reasonably affordable and with the right intensity that is suitable for you and your body with no side effects such as weight gain, rashes, dandruff etc.
Balding is irreversible. You will need to apply tonic, to at least maintain the "new" hair for life.