Assalah mu Alaykum i gave my word to my tenant that when I sell my house he will get the 1st chance

Assalah mu Alaykum I gave my word to my tenant who was staying in house for 20 years 3 months before I gave him a price 300k When the time came to sell i went back on my word and sold the house to another person for 325k as he was offered me more So my tenant got really angry with this because I went against my word I know I am wrong What is shariah ruling on this The now ex tenant says that I have to give him back 24 months of rental as he stayed in there for 2 months Though he still has outstanding balance of unpaid 6 months rent Only then maybe will forgive me He has given me 2 weeks to do if not then he is threatening me by saying he will report me to HMRC for not paying or declaring the rent payments to them He has recording where I have said I promise to sell the house to him so he is going to make viral to whole world to show my character to people of how I break promises Is this allowed What is the ruling on this to Please advise Jazakalla u khair Mehboob