I had a haematoma after an accident and awaiting surgery they're now saying it is a lipoma is that possible and what's worse as anxious?

Neither: I wouldn't really worry a lot about either. A hematoma is simply a collection of clotted blood which will typically resolve over time and is not dangerous unless it is pressing on a vital organ. A lipoma is a benign fatty tumor which generally does not cause any pain or problems and is usually removed only because of cosmetic reasons or because the patient wants it out.

Neither is serious: Neither a hematoma or a lipoma are usually serious conditions. Most hematomas get reabsorbed by the body eventually. Lipomas can be observed unless they are growing or are symptomatic. You don't need to be stressed about either condition but check with your primary care doctor if you have any concern.