"I met Angelina [Jolie] last night, and she kissed me right there," Aaron, 25, gushed to PEOPLE, pointing to his left cheek, at the fifth annual Children Uniting Nations conference in Washington, D.C., on Tuesday night.
"So I said, 'I'm not washing my face right there.' I almost passed out!"
Aaron experienced the giddy moment with Jolie and Brad Pitt at the Salt afterparty following Monday's premiere of Jolie's new spy thriller in Los Angeles.
"They were standing and talking to somebody, and Brad said, 'Oh, wow. Watch out!' " the 6-foot-8 actor says. "He came across the crowd to shake my hand. He was congratulating me on the movie and telling me how much he loved it. He brought Angelina over, and she gave me the big hug and the kiss on the cheek."
Along with the kudos, the megastar pair gave Aaron some advice about the business. While declining to share specifics, Aaron said it was "a lot of good advice. It was more personal."
Still, the young actor, who was attending a private dinner in Georgetown to kick off the annual Children Uniting Nations conference, has plenty of love left over for Bullock, his on-screen mom in The Blind Side. "I'm real happy for her coming back out from what she went through," he says.
Aaron hasn't met Bullock's son Louis, but he says the Oscar winner is surely a stellar mother already. "One of the key ingredients of becoming a great parent – either mother or father – is unconditional love for your child, and she has that," Aaron says. "She has unconditional love for everyone as a human being, and she's one of the most loving, caring people that I know."