can you use a regular needle for cross stitching?

It's not going to hurt your project any, but you may find it more difficult to thread. I've used both before. But I would make a point of grabbing some the next time I was out and I always make sure I have extra on hand for that very reason.

If you are using Aida cloth for counted cross stitch, you're better off using tapestry needles. You can use regular needles if you're VERY careful about getting the point into the holes, but the tapestry needles are easier.

If you're doing stamped on regular cloth, a standard sewing needle will work, but use a threader so that you don't fray your floss.

Get some embroidery needles next time you're at the store. They have much larger eyes and handle the floss much more easily.

You CAN but because sewing needles have much sharper points, you might find yourself stabbing the fabric more than usual. Next time you're out, buy packs of tapestry needles (those are the ones you use for cross stitch with the blunt tips) in different sizes (size 24 for 14 ct aida, size 26 for 16 ct) so you always have some on hand. They're pretty cheap. Also, if you were using 3 strands of floss in your tapestry needle, you might have trouble getting that many strands through the eye of your sewing needle.

If the eye is big enough for the floss to fit thru you should be OK.

If you can take a file to the point and dull it a bit. Then you won't be stabbing the fabric/aida cloth as badly.

When you're out next get a pack of x-stitch/tapestry/embroidery needles. Or a multi pack of Craft needles.

Have fun....