is ringing in a transformer bad?

so i just breadboarded this circuit along with a hand wound transformer.


https://www.maximintegrated.com/app-notes/index.mvp/id/1923


the circuit operates correctly and seems to function as it should, but i was just wondering if ringing in the circuit will cause any issues down the line? is there anything i can do about it? it is oscillating around 200khz to 300khz. the ic is a square wave oscillator with opposite pulses on pins 1 and 8. i attached a few pics too. pic 1 is the primary side.pic 2 is secondary and pic 3 is breadboard.

That ringing is larger than I would want but fine for a hobby project.
I have to prove my projects will not cause radio interference.

You have long wires in your bread board. This is a source of ringing.
It is in part a function of primary to secondary coupling.
In part it comes form capacitance inside the transformer and capacitance in the IC and diodes.

Good job you have it working!

It can be due to circuit stray capacitance and parasitic inductance (inductance that does not connect the primary and secondary) in the transformer. As ronsimpson noted, the long leads on your breadboard likely contribute to the problem. Try to make the transformer leads as short as practical.