Should I continue Studying?
One of life's little idiosyncrasy's is that information and skill goes hand in hand when it comes to furthering your career and increases leverage when negotiating for a new position or promotion.
So the answer is: "Yes, you have to further your studies if you expect to get far in your career". Employers are always looking for candidates that have the required skills, qualifications and experience. May truth be told that "knowledge is power" and to progress at a faster rate in your chosen career you will have to continue studying.
You don't have to do your PhD in any given field though. Rather try doing an advanced course in computer applications and learn how to be a whiz in the relevant computer package for your work. Take a class to advance your writing skills or improve your vocabulary. People say that the difference between the man on the street and a successful leader is a vocabulary of 1500 words.
Ongoing studying gives an indication to your current employer that you're willing to learn and possess an inquiring mind. If you have added to your skills since starting with your company and your colleague hasn't done the same, a promotion will be awarded to you instead of him.
A word of warning though. Be very careful when choosing the degree, diploma, or certificate that you wish to complete and even more careful when choosing the institution. Make sure that you go to a reputable institution whose qualifications are recognized.