Bubble after lip filler, what could it be and how can I treat it?

I appreciate your concern. Bumps are common after lip injections, as this area can be particularly prone to swelling. As you had more than one treatment in a relatively short period of time, it is understandable that you would experience these side effects. Rest assured the swelling should go down without intervention with a few days. In the meantime, you can use some ice on the area to manage swelling and discomfort. Always make sure you are working with a doctor who is both board certified and very experienced in using fillers to perform lip augmentation. While it might seem like a common treatment, precision is imperative to ensure a smooth and natural result. 

Looks like there are a lot of dynamic clinical treatments. For sure there are some missing segments in terms of your lip augmentation information provided. When you feel concerned, you should seek out another board certified plastic surgeon. The web is not the way to get your concerns addressed. Seek out a face to face meeting. This is important for you. Dr. K 

As you have had two treatments fairly close together I recommend allowing some time for swelling to resolve.  If after 2 weeks from the last treatment you are still having concerns, return to your injector for an evaluation.  Gentle massage of the area may be helpful in the meantime.