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I read your query and understand your concern.
As per your description, there was no headache, loss of consciousness, vomiting, or any symptoms apart from vision, and your head was hit on the right side. Now your observation about the vision problem is on the left eye, which is only in far vision. With such history, it seems unlikely to be due to head bumping.
Moreover, with history, we cannot tell the exact cause of this far vision impairment and cannot rule out any internal injury. There have been cases that develop internal bleeding after trivial injury too. To rule out your concern, I would suggest MRI (magnetic resonance imaging) brain, including orbits, and in-person consultation with ophthalmologists. Kindly revert for more queries.