Under eye bag only on one eye, how can I get rid of it? (Photo)

This should be correctable by a one sided lower blepharoplasty through a hidden internal approach.  Typically the recovery is very quick - Friday surgery can work on Monday.

I WOULD TRY FILLERS BEFORE GOING IN AND DOING SURGERY , THE DIFFERENCE BETWEEN FAT TRANSFER AND FILLERS ARE FILLER ARE LESS INVASIVE AND CAN LAST 6-9 MONTHS SOMETIMES UP TO A YEAR DEPENDING ON WHICH ONES. FAT TRANSFERS ARE USUALLY SURGICALLY DONE WITH LIPO AND TRANSFERRED TO ANOTHER AREA OF THE BODY. A FAT TRANSFER CAN ALSO BE DONE THROUGH A LOCAL AFTER SURGERY FOR A REPEAT FAT INJECTION. FAT INJECTIONS OR TRANSFERS ARE USUALLY MORE PERMANENT. THIS IS SOMETHING THAT YOU MAY WANT TO SPEAK TO YOUR DOCTOR ABOUT IN A CONSULTATION AND SEE WHAT YOUR OPTIONS ARE.

Thanks for you question. There are generally three methods to reduce lower eyelid bags and wrinkles.
1. Utilizing peels, lasers or any other ablative or semi ablative techniques to stimulate new collagen growth. Though effective, most people want to have little to no downtime and in order to get a very effective result with which most patients would be extremely satisfied, these techniques will fall short of their stated goals. These techniques are wonderful if they are utilized in an appropriate strength. 
2. Carefully injecting a temporary filler (such as Belotero® or Restylane®) underneath the skin in hollow areas with magnification. This could be quite effective but does involve the risk of producing irregularities and lumps and will necessitate a certain amount of bruising. A permanent filler such as Bellafill ® or even a fat transfer utilizing purified fat from your body are also options.
 3. Performing a simple surgery under local anesthesia called a pinch blepharoplasty. In this operation, a small strip of skin is removed directly underneath the lower eyelash line and results in a nearly invisible scar. The recovery is very rapid (a couple of days) and involves one single stitch which is removed in five days. This approach is actually the least complicated in appropriate hands and will produce the most consistent and significant of results in reducing your lower eyelid bags and wrinkles.