It looks like echymosis. Are you in any other medications like asprin,clopidogrel,or antiplatet drugs, anticoagulant therapy.
Could be due to injection site thrombophlebitis.
If pain,induration are severe get to dermatologist.
Keep ice pack 15 mins twice a day.tab
vitamin c chewable daily.
Thrombophobe ointment once a day over affected area