Thank you for the query.
Tissues swelling without blood collection (bruise
) should go away in a week or so. However if there is any blood collection, it can heal even few weeks. If the trauma was strong enough, broken bone is also possible. In such case, healing can take a month or longer.
You should know that even minor head trauma
can cause serious complication including subdural bleeding. That is why I suggest you to visit your doctor and consider head CT.
Hope this will help.