I am not sure if there is such thing as Master's degree in Human Resources.
But there is a MBA with emphasize in Human Resources.
To get into MBA you first have to take GMAT test and you have to score pretty high on it, since entrance to MBA program is really competitive.
Also to get into MBA, the school typically asks you whether you have a previous business experience (preferably in management setting). If you can somehow prove that you have a adaquate experience, you may be accepted into the program; if not, you will have to gain the appropriate work experience first.
So MBA is a good degree but it is really hard to get into the program. Also thing to consider is while you are taking MBA you won't be able to work at the same time (the program is very demanding), so there will be some financial loss there.
But if you absolutely hate the current job, the why not, go for it! you will have to study freallyhard though, if not during the program, at least to GET INTO the program