Fever is a rare side effect of using the topical cream Aldara and is found in 1% users. You can talk to your doctor and get the topical medication changed. For the fever take antipyretic and apply cold compresses. Also look out for other side effects like itching, burning, pain, headaches, sinusitis etc.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.