You need to open icons.png and replace my crosshair with the default one and then save the changes. You can do that with any photo editor app, i recomment you using photopea which is online and free. You can see under the comments for the steps that i posted to someone if is it any helpful

Yes!
You just need to replace the crosshair with an photo editing app
i recomend you to use photopea since its fast and it is on the brower.

A quick tutorial how to do it

-open your texturepack
-click on assets
-then on minecraft
-click on textures
-and then gui

there you will find a file called icons.png

there is where the default chrosshair is
drag that file and drop it in the photopea app
then just take one of the crosshairs of my pack and place it exactly where the chrosshair is (top left corner)
*not all the texturepacks are the same so you may need to remove the black areas arround it*
and then you save it with the same name always and you drop it back to your texturepack and you are done!

i hope i helped!