I'm trying to recall the title of a short story in which a sage, older space traveler tells his companion(s?) to "look, but don't touch" something suspicious on an alien planet, and saves the woman (from alien globules) after she disregarded his instructions by immediately shearing off her arm with some sort of laser... I read it in the 1980s. It was in book form and may possibly be a tale from Larry Niven...
Not a perfect match but could be The Manna Hunt by Charles Sheffield, one in a series of short stories featuring genius physicist Arthur Morton McAndrew and space pilot Jeannie Roker. In this story they transport arrogant government official Anna Liss Griss (plus aide) to a comet found to have a liquid water core with weird single-cell life described as fuzzballs or snowballs. Griss defies an order/warning from Roker and touches one snowball. It "cling[s] to her finger" until knocked loose, then the finger continues to swell. McAndrew severs her arm with a "construction laser", explaining that the organisms reproduce by "swap[ping] sections of DNA" which he believed had entered her bloodstream and could cause a fatal immune reaction.
This story is listed as published in Analog Sep 1982, and apparently first collected with the 3 previous ones in June 1983, which fits the time; I have the later 2000 collection by which time there were 9 stories. I would say Sheffield's style is pretty similar to Niven.
Amputations are a minor subtheme of this series: McAndrew's hand is severed (and lung damaged) in an attack by violent rebels in the first story, Killing Vector, and a finger is cut off by Roker to rescue him from super-compressed matter in the ninth, McAndrew and The Fifth Commandment. But such injuries are treated by "regeneration", not explained here but apparently completely successful; it may be the consciously-directed "biofeedback form change" of the same author's BeyWolf/Proteus series. Highly compressed matter is another subtheme, see Looking for a sci-fi novel about a ship with a neutron star at one end to counteract acceleration .
Note: I don't see need for spoilers 30ish years out but if anyone disagrees feel free to add.