can i apply for waranty if after 6months my batteries condition is 89%?

Make an appointment at the Apple Store or take the phone in to an authorized Apple service shop to have the battery checked and tested.

You can find a list of authorized shops in your area using this link: Find Locations

It won't hurt to ask, but Apple will not normally replace the battery unless it has declined to less than 80% in the first year.

While Bob Timmons is absolutely correct that Apple will not generally replace a battery until it drops below 80%, they may if there is something else wrong with the battery. Eleven percent is a pretty large battery drain for six months. You might want to contact Apple and have them run diagnostics. If they find that the battery decline is outside of normal parameters for some reason, they may decide to replace the battery.

Genius Bar Reservation and Apple Support Options - Apple

ETA: Bob Timmons has edited his post since I posted so mine no longer reflects his original reply.

As far as signing-up for AppleCare+ you’re too late …

… there’s a 60-day “window” to do so immediately after purchase.