After ejaculation, some semen contacted a cut on my hand, about 3 days later my semen seems quite clear and watery. is there a chance my body has developed anti-sperm antibodies?

Anti sperm antibodies do not form so fast and usually not in that manner. It is not from this incident. If it remains like that see a urologist.

No, you have not formed anti-sperm antibodies. Give masturbation a break for a week or so and your semen may recover. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV and Covid vaccines. Wish you good health!