Toenail fell off and now big chunk of fungus. could you help me?

Many ways...: Topical solutions, oral medications, laser treatments, surgical removal, homeopathic remedies, etc. The most used treatment is oral Lamisil (terbinafine) tablets once daily for 90 days. See a podiatrist for what may be best for your specific needs and expectations.

Don't worry.: Toenails very commonly fall off, sometimes due to fungus, sometimes due to trauma. If your toenail grows back (it usually does but not always), have a doctor take a sample and send it to a lab for identification. If it's a fungus, your doctor can help with treatment options.