how can i convince my boyfriend to use lubrication when he materbates?

he doesn't do it very often but when he does he ends up rubbing himself raw and I'm getting worried about it. I don't want him hurting himself like this. i have mentioned to him before about possibly using lotion of some kind but he just laughs at me because he thinks its a funny topic coming from me. is there any way i can convince him to use a lubricant of some kind?