What to do if i had an injury in my left testical and now it is atrophied and my sperm counts are low how i can trat it?

No treatment: As far as the atrophied testis, it is not recoverable. Sorry. If there are issues with fertility (trying to have children for a length of time), then your remaining testis may need some help. Make sure there's no varicocele, and possibly some medications can help, but you need an exam, semen analysis and possibly imaging and/or labs to see what the issue is.