Change in internal engery = heat added - work done by fluid
(This is literally just the conservation of energy)
In your scenario, you are compressing the gas. Work done by fluid = boundary work = (pressure)(change in volume). The change in volume is negative and so boundary work overall is negative. No heat is added. Thus we have it that the change in internal enerfy is dU= -(boundary work) which is a positive quantity.
Internal energy U is a function of temperature, and so a positive change in U means U increases means T has increased.