Dear @Arb,
To directly address your worries, there is very very low chance that such a small amount of blood (trace and invisible) could transmit to your colleague.
Yes, Hep B is more resistant than some other viruses, but it is still susceptible to microbicides including alcohol-based hand rubs: High Environmental Stability of Hepatitis B Virus and Inactivation Requirements for Chemical Biocides
"All hand disinfectants demonstrated virucidal activity at the ready-to-use concentration and inactivated HBV to undetectable levels "
I am not sure there has ever been a transmission event between adults recorded with such a low level amount of fluid. Also remember that the great majority of adults will clear the infection without any issue (or are vaccinated so this isn’t a problem), even more so if the initial infectious dose is low.
You might want to consider using hand lotion, so your skin is less likely to crack (this may be due to all the alcoholic hand-rub we all use now drying out your skin) and also using a band-aid to cover your wounds (which would also help limit any small risk of transmission).
Hope this helps,
Thomas