I suffer a pain on the left part of my lower abdomen and sometimes i felt like there is a bulge there.

As above: To make sure nothing serious is going on , see your PCP for evaluation and work up.

May be a hernia: You need to see your doctor, most likely it may a hernia , after examination will tell you , what that 'bulge' is and advise you to relive pain and cure.

Abdominal Pain: Your description is quite non-specific and could be due to a myriad of issues, including sigmoid colon pain and distention, or ovarian/pelvic problems, to name just two. Since the bulge comes and goes, it is likely not a tumor, and i would bet on a digestive etiology. If the symptoms don't clear, you might want to check with your doctor.