I concur. ‘Internal use of disinfectant UV light’ is exactly what I understood President Trump to mean too.
Additionally, when PT said “through the skin or in some other way” he spoke the words “in some other way” hesitantly, as if casting around in his mind for the best term for that medical procedure and not finding it.
With the benefit of much time and no pressure, I think the term PT was looking for was ‘intubation’ (or possibly ‘inserted through a breathing tube’). Those terms are used in the Healight video outlining the process.
A bit later PT just goes with “injection”, not having been able to remember the better term ‘intubation’ in the pressure of the moment.
https://greatgameindia.com/ultraviolet-light-technology-to-treat-coronavirus
https://youtu.be/MQaRLkViXNA
From the video: “Healight is inserted into the breathing tube of an intubated patient.”