Entering tenant apartments

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I currently live upstairs in a multi-family with my tenant on the first floor.  I had a plumber in the tenants apartment this week and he told me it was "dirty" but did not specify.  All the doors were shut when he went in.  I hear banging at night.  In the lease it says the landlord is permitted to go into the apartment with 24 hours notice.   The tenant has occupied the apartment for 5 months.  Should I go in?  If so, when the tenant asks why, what should I say? 

Thanks for the help!