I had hernia repair 2 weeks ago. Where I have been stitched up theres a raised hard lump all across where the cut was, stitches should have dissolved?

Normal. Perfectly normal. Inflammation in tissue related to surgery. Will resolve over next couple of months as will the dissolvable suture.
Probably nl. After an incision is made in the skin and when things are sewn back together underneath the incision a hard ridge of tissue develops. This is genly a nl process of healing ie a ridge of induration. This will take weeks to dissolve. Any concerns see your surgeon to be sure nothing serious is going on.
Normal early scar. Most surgical wound repair is done in layers. If no skin sutures or staples were placed then likely all the repair was from the inside and the half life for the sutures commonly used is between 40-60 days therefore the ridging that you feel should be normal. As wound healing progresses the body lays down scar tissue and this takes 9 months on average to mature, so be patient during this process.