I’m with you, that is spooky! 
It would depend on the type of cleansing and the exact words/intentions set during the ritual, but generally cleansings are to remove bad or stale energy. If you’re worried something else might move in to the newly freed space, a follow-up protection spell, barrier, or ward could help lay those fears to rest.
As for irritating any entities already there, it’s hard to know how something might respond. You might want to try to get a more solid read on it before doing any work. Do you have a favorite method of divination? Or, if you feel safe doing so, do you think you could try to communicate with it? Once you have a more clear idea of who/what it is and what it wants, you’ll be in a better place to decide how to handle it (or if it needs handling at all - some house spirits can be beneficial).
Thank you, Kat - wishing the same to you! And wishing you good luck with whatever spookiness is happening in your home. I’m sure you’ll work out a way to move forward 