The 19-year-old started his second Premier League game since joining the club in January, and his header shortly after the hour mark was his second goal in as many games.
It also took him to two goals and one assist in his three appearances so far in a Bournemouth shirt.
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But it was not the best first half for the Brazilian, or the Cherries, as a flat showing saw them create little.
They went into the break trailing by a goal as Rayan perhaps showed his inexperience by attempting to dribble the ball clear from deep in his half, and Jarrad Branthwaite stealing in to pinch the ball and going down under contact from the winger.
(Image: Peter Byrne/PA Wire)
The penalty was awarded and duly converted by Iliman Ndiaye.
After the break, though, the Cherries grew into the game and took advantage of a good spell around the hour mark, scoring twice in three minutes to take the lead, which they held onto for a 2-1 victory.
Shortly before the first of the Bournemouth goals, Rayan felt he should have had a penalty after he was brought down by Vitalii Mykolenko, but it was waved away.
But he headed home the first goal as he rose brilliantly above the Ukrainian to power the ball into the back of the net from a pinpoint Adrien Truffert cross from the left.
On Rayan’s performance, Iraola told the Daily Echo: “I think it's obviously a mistake from Rayan [for the penalty], but we have to accept this kind of mistakes with him, with the young players, because he's coming to a new league, he's 19.
(Image: Peter Byrne/PA Wire)
“He knows he cannot do this in his own box, but I think they've been smarter than him.
“They just touch the ball in front and it's a pen, but he has shown character. Because I don't think he gets too affected by the pressure. He's continued being a threat.
“I think second half with Mykolenko, I think it was another pen in the other side, but continued to score the goal. I finished happy, even with the mistake.
“I think it's a good learning experience for him and it hasn't cost us points at the end.”