Hello, I recommend that you immediately replace your battery if it is swelling. I had a similar problem where the battery started changed the shape of the laptop case... I ended up getting a new battery.
"Swollen batteries often occur as a result of over charging. This can cause a chemical reaction in the battery that can lead it to grow and eventually split. If you think your battery is swelling, you might notice the case fitting incorrectly. Open your device and check it immediately. If you notice any swelling, you should dispose the battery safely and seek a replacement from the manufacturer."