The Nature Boy tells us he's not only healthy and ready to get back in the ring (in fact, he says he's been by cleared by doctors) ... but he's also back on great terms with WWE.

Remember, Ric  told us in September he had some problems with WWE superstar Becky Lynch using the nickname, "The Man" ... because Rick says he owns the rights to that term and thinks the WWE should pay him for it.

But, when we saw Ric at LAX on Thursday with his wife, Wendy Barlow, Flair said things are definitely cool now ... and he chalks it all up to a case of "agree to disagree."

Now, Ric's focus is on wrestling again ... and he's teasing a major showdown with a major superstar at Friday's "Smackdown" debut on FOX.

"I'm cleared for anything," Ric says ... less than 5 months after undergoing heart surgery. Flair had a new pacemaker installed after experiencing some heart issues in May.

"I could be in the main event [Friday] night. It could be me and [Steve Austin] or me and The Rock or it could be bigger than all of that with me and Hogan!"

He left with one message for the Hulkster ...