Tyrod Taylor says the punctured lung he suffered before a game last September has NOT had any lasting impact on his health ... and now, he tells TMZ Sports he's ready for free agency.

You'll recall ... Taylor was the starting QB for the Chargers until Sept. 20 -- when team doctors botched a painkiller injection and injured his lung just minutes before kickoff against the Chiefs.

31-year-old Taylor was rushed to the hospital ... but the injury put him out for so long, star rookie Justin Herbert took the signal-caller reins and never gave them back.