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There is nothing to worry, it will get fine in 1-2 days. You can apply a thin film of neomycin
oitment on the bruise
. If it is painful you can take an analgesic
Do not scratch or rub. To reduce the inflammation and hardness you can apply thrombophob oitment, it will aid easy blood circulation and reduce the swelling.
Do not let the bruise get infected. However, if you see any pus forming, you should take antibiotics to help wound dry up and get well early.
If wound remains the same get clinically assessed and treated. When you take the next shot, do not take it in the same spot, take care.