It is normal to experience some swelling after any filler treatment (this is generally with any injections to the face).
I assume you are referring to excessive swelling out of the ordinary. This could be too much volume injected in a small area or uneven placement of filler resulting in unevenness and lumpiness. All those could cause lumpiness and swelling.
For this, we can do an 18g puncture and try to express the excessive ellanse or we can have a trial of oral corticosteroids like Prednisolone, failing which, other more invasive measures may be needed.
If ellanse is injected intradermally (in the superficial skin layer) where it’s not supposed to be, that may cause granulomatous/excessive inflammatory reactions.
Having said that, prevention beats cure and it’s best to look for a very experienced ellanse doctor as it requires a lot of experience and knowledge to use.