Dust
Remove dust from your painting regularly to avoid it building up. Dust can contain certain acids which can erode or dry out the artwork. You can periodically remove dust from the oil painting with a soft brush or lint cloth. Don’t use feather dusters or dust cloths as they may scratch the painting surface. Don’t use a damp cloth or cleaning chemicals.
Aerosols
Aerosols or fine mist cleaning products should not be used near a painting. If you do use them, then spray them on a rag away from the painting, rather than spraying directly onto nearby surfaces.
Varnish
Your painting has a coat of varnish on top of the oil paint. Varnish helps to protect from dust and pollution reaching the surface of the paint and damaging it. It creates a barrier to prevent removal of paint/colour when cleaning. If you ever need to have your painting professionally cleaned, then the varnish can be removed and replaced without disturbing the paint.
A new varnish can be applied over the current varnish without any need to remove it first. I have used retouch / gallery varnish on all of my paintings.
Oil paintings are durable - just take some care and you’ll enjoy your painting for generations.