Landlord trying to sandbag me under cover. Security Deposit

Can your previous landlord sue you ten months after you have moved out and into another place if you left in the proper amount of time (lease was up Dec 31 - I was out by the end of the day turned in keys Jan 1/ 2) and if I gave them my forwarding address, (they did not send me a bill to dispute) and I did not get back my security deposit can they sue you for damages to the apartment when right after you left two or three weeks later rented it to someone else? They have already put this on my credit report which made it bad for me being that I'm trying to start a business and they want $1400+ not to mention they kept the $300 security deposit , what should I do??? Please help.