Unknowingly giving up my time to the theatre hall for a holi and easter celebration

I am a lecturer/ tutor by profession. A lecturer asked to use my lecture theatre time for something. I did not understand or listen to her properly what she wanted to use the lecturer theatre for. Without listening properly I allowed her. Later on, i realised it was for Holi celebration and Easter celebration. Have i committed a sin? What do i do to ask forigiveness from Allah on this? But then again, it was not entirely on me allowing it or no because that lecturer threate is owned by my employer but I was only scheduled to take a class during that time.