Oh don't cry gail. This is typical, even to be expected. Anytime tissue is damaged it forms some scar tissue.
The dr did an incision in your skin to gain access, damage, so a surface scar. He had to cut through some muscle in the abdominal wall and then sow it back up afterward, damage, scar tissue and of course he had I am sure to remove the kidney, more cutting and more scar tissue. The problem with scar tissue is that it doesn't stretch like muscles, tendons, blood vessels, etc. So after the tissue starts to heal the scar tissue forms and begins to stiffen. This means that if you twist, turn, bend, etc it pulls not only on your sutures but also on the scar tissue and this causes pain. Happens every time. the dr gave you some restrictions on physical activity, such as a weight limit of say 10 lbs. This is to keep the stress off the fresh incision while it heals. Be sure and follow the limits he set and do not overdo it. Incisions and scar tissues take 4 to 6 weeks to toughen up. During that time take it easy. When the dr blesses you will full activity then you need to start stretching. Find at what angle of twist, bend, rotate that you feel the discomfort. A few times each day stretch that area. Do not stretch enough to cause bad pain, just enough to pull on the area until uncomfortable. Relax and then repeat several times. Usually the scar tissue can be stretched out over a 3 or 4 month period and your range of motion can return to normal with no pain.
This happened to be after my hernia surgery. After 4 weeks the dr said I was cleared for physical activity with no weight restriction. I had a lot of tightness in that area and could not twist or bend without discomfort. I stretched out the area 2 or 3 times a day and within a couple months could move like normal with no discomfort. Your surgery is more involved than a hernia repair so it might take longer. Remember, time and patience...but nothing to worry about, perfectly normal.