Blurred vision caused by a lot of reasons, concussion is one of them. Concussions are graded on a scale of One to Three: Grade 1. Lost memory; Grade 2. Difficult recalling the events but didn't lost memory; Grade 3. Slight concussion, only feel uncomfortable, such as blurred vision. The Grade 1 and Grade 2 must need treatment, but for the slight concussion, you just need have a good rest and wait for several days, it will disappear naturally.
It is not known how long blurred vision last after a concussion. It depends on how seriously your head hurt. It can last weeks and you should go to see a doctor as concussion without treatment can cause some other serious problems. You should have your head examined and perform CT scans or MRIs. You should be taken care and be observed by medical staff. Once your brain has got well, your eyes will get well as well.
Well, sorry to hear that you have got a concussion due to some reasons. However, generally speaking, it would take you a while before you feel better, about a couple of days. Therefore, you have to get some immediate and effective treatment and care, since it is quite serious to some extent. Actually, the blurred vision you suffered is temporary and absolutely treatable.