Captain America's been recovering from getting hit in the balls a pelvic contusion this week ... which came after making contact with Iran's goalkeeper after scoring the game-winning goal.

CP said Thursday he was taking it one day at a time ... but was doing "everything in my power" to make it out on the pitch on Saturday.

Pulisic also clarified his injury was, in fact, a pelvic contusion ... saying, "I didn't get hit in the balls."

"I'm alright. It was very painful. That bone is there for a reason to protect you and I hit it well. I was sore."

He posted a Snapchat from his hospital bed after the 1-0 win on Tuesday ... promising he'd be back for their next match -- but admitted the pain was pretty tough to fight through.

The 24-year-old is holding up on his promise ... 'cause Pulisic is now good enough to go as the Red, White and Blue head into the round of 16.