Regretting after requesting a salary at new job?

I am in a big dilemma right now and I think am stuck with no way out. If any, please provide me a solution to my problem. I had a job interview with 8-10 interviewers with a company in another city than I currently live in. It seemed like all the interviewers liked me and so, finally, the director came in and she offered me a job and asked for a salary I want. My bad, I requested a salary (which was 10% raise from my current job) but from the expressions of the director, it seemed to me, they liked me so much and thought of me as a very valuable resource and expected that I would ask much higher salary than that. She immediately approved the salary I requested. Now I kind of think, I would easily have gotten 25-30% more than my current salary. Can I do something about this? or Once offered a job, it cannot be changed? Please advice.