Will I need to change my acne regimen if I've now developed large acne cysts?

Yes. If you are getting large cysts amd are on antibiotic they may need to be changed. If however you are not taking antibiotic then they can be added to the regimen. If your acne is resistant to antibiotics, Accutane should be considered after speaking to your dermatologist.
Information. If you have not used it before, now might bet the time to consider accutane. Consult your dermatologist.