If you stay away from simple carbs (eg sugar and white flour items) and have a small portion of good quality bread, pasta, rice or other grains you should not have cause to worry. A small to medium serve of potato is no problem either (depending on what's in/on it). If you load up on carbs you will probably see a little weight flare up tomorrow, but if this is a one off meal (like a once a week "cheat meal") then just enjoy it. Your weight will fluctuate all the time - but be on a definite downward trend if you are dieting and exercising for weight loss - the key is not to panic and give up - just expect some variation.
. I had my once a week cheat meal a couple of hours ago - Italian style pizza. My weight will be up tomorrow (probably about 0.3kg) but back down by Sat.
Have a nice night out!