Tennant now smokes, what to do?

[Silvia B.]

Last year when I advertised for my rental I stated "No smokers, no pets".Applicant stated on his applicantion that he does NOT smoke. We even talked about this in our interview with him, also. Although my lease states "no pets" , I failed to include no smoking (thought I did but now see that it was omitted in error). The lease does state that tennant will leave the home in same condition that it was in when first rented, except for normal wear/use.
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My non-smoking tennant moved in last November.Last month he started dating a lady who smokes and now he has begun smoking. She does not live in this home.
The other day he approached me and told me that he was honest with me when he first moved in (that he didn't smoke at the time) but has since picked up this old habit. "My girlfriend and I are trying to quit and neither of us smokes in the house."

So what now? He is a great tennant otherwise, keeps place very clean and always pays before the rent is due. Do I just wait until the day he moves out and subtract from his security deposit any costs that occur due to cigarette smell in the house, if there is any?
Learning from my mistakes...