If you have homeowner's insurance with liability coverage, you should be able to have an attorney retained by your insurance company defend you against the allegations in the suit. You can check with your agent or contact the insurer directly. There are timelines in your policy that require you to notify them, so check on that first.
In the event you do not have coverage that would cover your defense, you should consider speaking with an attorney about the claims made against you, the injuries sustained and other factors, to determine your potential exposure. Although virtually anyone can file a lawsuit or counterclaim, the specific facts of each case determine the legal liability and likelihood of success. There are many variables that determine whether you may be liable to a tenant for injuries sustained on your property and the amount of any damages.