18m, do floaters caused by a head injury disappear by time? If yes, how much? If not then is there any way to cure it completely or atleast improve it?

Traumatic floaters. Floaters following head injury may be serious or not significant. You should have a dilated retinal exam by retina specialist to rule out peripheral retinal breaks which could result in retinal detachment. Watch out for retinal detachment signs of 1. Lightning flashes, 2. Shower black spots going in many directions and 3. Field defect or curtain fold in visual field. Good luck!