You could be having a visual migraine without pain but I doubt it.
There are many things we notice after a concussion that we think are from the concussion but are really just something that we did not notice before the concussion. The changes in how the brain filters out aberrations and distractions in our senses can cause us to NOTICE things that we never noticed before.

Many will notice floaters and become alarmed. But, 999 times out of 1000, those floaters are normal and it is just that we never paid attention to them because our brain was better at ignoring them.