Loic Remy opened the scoring for the visitors after 14 minutes but Julio Cesar's fumble allowed Gaston Ramirez to level on the stroke of half-time.
QPR rallied after the break and Jay Bothroyd prodded home late on to earn an invaluable three points.
Pochettino, celebrating his birthday, said: "We have to accept that because we made some mistakes.
"We've tried very hard. We've put in a great effort to try and get a different kind of result.
"But because of some mistakes we have made and their goalkeeper's intervention a couple of times we didn't get a positive result."
Saints will monitor the fitness of Adam Lallana and Danny Fox this week after they were substituted with injuries.
Pochettino added: "Adam Lallana had a knock after coming together with another player on the neck and that is why he couldn't continue.
"Danny Fox had a knock on (his) quadriceps, which led to him being substituted as well.
"We do not know how serious it is. In the next couple of days we will do the necessary analysis."