The Republic of Ireland's record scorer had been linked with a short-term deal at QPR during the MLS close season - having made a similar move to Aston Villa last year - but said he was focused on recovering full fitness.
He told Sky Sports: "It's been a long season, with the Euros and what have you.
"I've a few little niggles that need to be sorted out so I don't think at this moment in time it would be right for me to go anywhere.
"I had another year left (on my contract) and they offered me a new contract at the end of last season. I've just signed a new two-year contract."