Should my foot still be sore 6 months after breaking 4&5 metatarsal?

Pain. Yes your foot can still be sore at times. But if pain is intense you need to have another x-ray taken and re-evaluation of the fracture site by a podiatrist. Furether tratment could be indicated.
Post fracture. Many times after a metatarsal fracture a foot can stay sore and swollen for months. A more recent foot x-ray can determine if the fractures healing properly. Sometimes due to movement of the fracture site a non-union fracture can develop which can cause continued pain. Have it checked by your foot specialist.