Definite plug:
The small gap between the top of the base and the top of the ring is very easily filled with wood filler in a squeezy tube (blob a bit onto your palette and stuff it into the gap with an old brush). Then PVA and/or your usual basing material to blend it in.
No need to prime, especially if painting black as PLA takes paint extremely well. I would suggest a coat of varnish once painted though.