OK, stretch the right hand needle over to meet the left hand needle and start knitting with a new ball or new end of yarn. Leave about a 6" tail to weave in later. The first few sts may seem a bit loose but you can always snug them up later.
You should have enough space to use the right hand needle but if you don’t have enough play because of the solid stitch holder, transfer the sts to some waste yarn. Do this by threading a tapestry needle with waste yarn and threading it through the sts, then tie a knot in the waste yarn so the sts can’t fall off.