Purchaser sueing seller for partial cost of lead abatement

[Abul Miah]

I purchased a rental property in detroit back in 2020 october and in 2021 October i sold it. In 2022 of May the purchaser is saying he is gonna sue me for 4k to help him pay for some of the lead abatement cost. Me and the broker signed a lead paint disclosure that stated we had no knowledge of any lead in the house. I don't know if he did any home inspection before he purchased the house from me. Is this a legit lawsuit I don't know if he can sue me since we had no knowledge and he purchased the house already. If i can get me some guidance that will be helpful thank you all