You can certainly attempt to fix damaged credit issues on your own. The process can be hard work. It will require your time, patience, diligence and perhaps some aptitude for understanding what the credit bureaus and collection agencies are required by law to do.
You may want to consider spending a portion of your stimulus payment on a professional, reputable credit restoration company to assist you along the path to better credit. A well-qualified credit restoration company will provide you with important guidance as to how to identify and address negative items that appear on your credit report, help you to maximize your credit utilization, teach you how to acquire and properly utilize a secured credit card, and help you with negotiating collection accounts.
The credit restoration company that you choose should also be reasonably priced. This will allow you to use only a portion of your stimulus check to pay that company’s fees while leaving enough money remaining that can be used to do things like obtain a secured credit card or pay off derogatory accounts.