Its been two weeks since my friend injured his jaw.what are the symptoms of mandible hairline fracture like on the left angle of jaw?

Depends: Clinical examination would include assessment of the occlusion (bite), tenderness to palpation of the muscles and jaw , resistance movements (both opening and closing), and manipulation of the jaw. Also, tooth position/looseness would be checked. Radiographic imaging would include Panoramic and 3D scans. Some may add a lateral Ceph. See a specialist - Oral Surgeon- for evaluation. Good Luck.

Pain, swelling: Pain, swelling, bruising.....colour change, purple-blue-greenish yellow-yellow...

Varies: The term "hairline" fracture" is usually used to describe a fracture that has not resulted in displacement of the segments. Often the occlusion is normal. Swelling may be minimal. Often the jaws are not wired or plated. The patient is placed on a non-chew diet. The patient is watched closely by the oral surgeon to make sure the fragments do not shift.