Personal hotspot secure?

I’ve just had to update my TomTom sat nav and these devices now need to link with a mobile phone for RTTI and speed camera info.
To link the two I had to switch on personal hotspot on my phone but I’m now concerned whether other people can access my phone as well?
The two are linked with Bluetooth as well now and I thought that perhaps I could switch off the personal hotspot and use just Bluetooth but when I switch personal hotspot off I lose Bluetooth.
Does this mean I’ll have to remember to switch personal hotspot on and off again whenever I use my TomTom? My last TomTom didn’t need to link with the mobile for these services.
Sorry if I sound really dim but I’ve no idea what these things are or do or whether they’re secure or not. Thanks in anticipation of anyone being able to help me.