If your hymen has already broken but you haven't had sex, will sex still hurt the first time?

Maybe. Not all women have a funcitoning hymen. Due to many factor, the hymen may have been "broken". Pain with sex can be multifactorial. First time sex may be painful due to many reasons. Those can be anxiety, sexual stimulation, size of the penis, lubrication, any pre-existing anatomical problems, etc. Be careful, be informed, be protected, be patient and be responsible.
Probably not. Should not be painful in most cases provided you are sexually aroused so that your vagina is "wet", your partner uses lubricant and insertion is slow and gentle.