Welcome to the forum , teddysmith1952 .
You should be able to make very slight adjustments to the pendulum weight position , in order to get the time 'tuned in' better - shorter swing = faster , longer travel = slower .
In the event your pendulum is non-adjustable , the procedure is individual to each clockworks manufacture & I won't go into that on this posting - I don't want to give you harmful suggestions here !
I'm assuming that your clock used to chime ( two weights - one for clock , one for chime ) .
Blowing off dust in a clock mechanism sometimes (often) causes particles of said dust to lodge in places where they shouldn't be , and can jamb mechanisms that were once 'free' .
Usually it's not a good idea to do to internal clockworks , unless a person is experienced at it .
A cleaning usually includes lubrication after the works has been 'cleaned' , with lubricants designed for the purpose (no WD-40 , etc.) .
Perhaps you've disturbed/repositioned a trip lever/mechanism , or over-wound the chain cog (or assembled it backwards) when you removed and replaced the chains .
It's a good idea to test both the chime & time functions , prior to reassembly .