Dull areas after staining wood

I stained an old table that I had stripped and sanded and a couple areas on the table top are dull. Is there a way to brighten it up to match the rest without having to sand it down and stain again?

Dull in sheen or dull in color acceptance of the wood?

Sheen

Tell us a little more about it. What was on it to start? Any stains or discoloration before you started? How did you strip it and with what? How deeply did you sand it? What did you stain with? I assume, from the sheen comment, it was an all in one product. How many coats? What did you do between the coats? What did you use to apply it?
What temperature was it and humidity when you let it cure?

Lots of questions, but it will help give you answers.

Don't have anything to lose

by just starting with a coat of shellac on top of that stain to see if it evens the sheen out some. About anything will stick to shellac so when you go to apply whatever finish on top of that it'll work just fine. If it still doesn't look right it's really easy to remove that shellac with sanding.

I'm wondering if you might not have sanded the entire top with the same grit paper or not as evenly prior to staining maybe?

Places where the wood grain changes, like a knot or something, will be rougher by nature and thus be duller.

On my cabinets, another coat or two of top coat evens it out.

I stripped and sanded like normal, buuuut I did stain it on a hot day outdoors and maybe the sun dried it a little too fast.

I have not put a top coat on yet because I didnt want to have to deal with removing if it wasnt going to fix the dullness.

There are no knots or anything in the spots. I just think it dried too fast in some areas, if that makes since.

If it was in the sun and hot, especially a larger piece, you may have some areas the stain did not get rubbed evenly before it dried and absorbed.

Typically, if you still have much of a sheen after just using a stain and it drying, you have a little too much. The stain should absorb completely, leave an even color and dry to a dull finish. If you are using an all in one, that is a different deal.

When you stripped it, was there any difference in the coloration or texture in the areas that took the stain differently?

I have stripped paint from a piece that was originally stained and fount that the finish under the paint had worn and allowed oil or grease or some such to absorb through. That was why it had been painted to begin with. A few of those got repainted because the staining was deep and I could not even out the color.

There is no stickiness so I dont think its due to having too much stain on it.

Its not shiny finish. It actually looks really great, with just a couple areas. Really the untrained eye probably couldnt see it. I just know its there because I did it.

I put a lamp on it and you really cant see the areas anymore.
I guess Im just going to have to be more careful about where and when I stain.