I’m a bit rusty on this and a diagnosis from a runner orientated physio should be sought, but here goes: true shin splints affects the tibialis anterior muscle which dorsi flexes the foot (lifts it), in its most severe form it tears the muscles connective tissue away from the outer layer of the bone causing fractures. You may have this, or you may have a lesser degree of aggrivation such as inflammation of the connective tissue and or muscle tightness.
The cause can be too much too soon, of volume (duration, frequency etc) or intensity (impact, increased exertion etc). You need to stop or significantly decrease your causes.
Use ice for short bursts (<10min) frequently throughout the day, in the acute stage ibuprophen may reduce pain and swelling, if advised to stretching the muscle requires it to be lengthened, I have found that by adopting a standing quadriceps stretch position and then adjusting the ankles range of movement until it feels right worked of me.
Get your footwear and gait checked at a proper running shop, build up your runs on a treadmill, run on soft surfaces, avoid tarmac but above all get some professional advice from a running expert rather than some rusty old git on a cycling forum.
PS: 10k’s are where its at for injury prevention, not having to dedicate your life to training and having more frequent events.